Comparison of levobupivacaine versus ketamine and levobupivacaine for ultrasound-guided adductor canal block in patients undergoing unilateral total knee replacement: A randomized, double-blinded study.

Background and Aims: Ultrasound-guided adductor canal block (ACB) has been increasingly used for postoperative analgesia in total knee replacement (TKR) surgery patients. We hypothesized that the addition of ketamine to levobupivacaine in ultrasonograsonography (USG)-guided ACB would result in prolonged and better postoperative analgesia in patients undergoing TKR. Material and Methods: This randomized prospective study was conducted on 90 patients undergoing unilateral TKR. In Group LK (n = 45), levobupivacaine 0.25% plus ketamine 1 mg/kg (total volume 20 ml) was given, and in Group L (n = 45), 20 ml of 0.25% levobupivacaine was given. The primary objective was to compare the pain-free interval, i.e. the time until the first dose of rescue analgesia, between Group LK and Group L. The secondary objectives were to assess the amount of rescue analgesic, pain scores, and complications. Results: We observed that the time to the first dose of rescue analgesia in Group LK (9.33 h ± 2.17) was significantly longer than in Group L. (5.02 h ± 1.63) (P value = 0.001; Cohen's d = 2.243). The total dose of rescue analgesic was significantly lower in Group LK (188.89 mg ± 48.72) compared to Group L (271.11 mg ± 50.55) (P value = 0.001). Patients in Group L had significantly higher numerical rating scale compared to Group LK at rest at 4, 6, and 12 h and on movement at 2, 4, 6, and 12 h postoperatively. Conclusions: The addition of ketamine to levobupivacaine in ACB resulted in prolongation of the pain-free interval, decreased requirement for rescue analgesia, and better pain control during rest and movement.